Preparation of alkali phosphates



manner. As a rule also, the yields a e defifi substances which react in the aforesaid manner bonates at elevatediemperatlli'es,With he. a of tinuously or discontinuously removed from the the W813 decomposition PI'OCBSS, WhiCh'iS carried afore -menfign passage of, xygen. orfloxygena 5 ia1ka1i hydroxides or carbonates for the converexample, trisodium phosphate, as alkali-yield- Patented Nov. 14, 1933 it a r U IT D STATES PATENT-1 OFFICE i PREPARATIOYN'OF ALKALI PHOSPHATES Otto Laubi, Paris, France, assignor to 'Bozel Maletra' Societe" Industrielle De Produits Chimiques, Paris, France, a company of France No Drawing. Application June 15,1933, Serial No. 676,015, and in France May 26, 1932 12 Claims. (01. 23-407) It is known that ferro-phosphorus can be consion, the operation can also be carried out with verted by calcining roasting or fusingin the presthe aid of other substances, which yield alkali ence of alkali sulphates or alkali carbonates and under the c-onditions of the reaction, such as 321, in this way alkali phosphates be produced. A kali' silicates, alkali 'aluminates,' 'orga'nic alkali 5v process is also known, according. to which iron salts or the like. The resulting liquorscan be 6 phosphate is first obtained from ferro-phosphorus worked up in known manner to alkali phosphates by roasting and the iron phosphate then con,- after the completion of the process and separation a 'verted with alkali carbonate under pressure. A of-the solid constituents. 1

further processv is known according to which It has. been further found according to-this 1. 0; phosphides are heated in the presence of aqueous invention that it is particularly'advantageous to, alkalies to temperatures above 1G0 C. lparticucarry out the conversion by subjecting the preflarly' to temperatures of from 300 to, 350 C. erably finely comminuted matter'to thorough whereby alkali phosphates and free hydrogen are mechanical mixing, for example inshaking or formed. .All these known processes, however, are stirring autoclaves. 'In this way not only can 3! of slight practical importance S ce ey" the entire process be advantageously accelerated require high temperatures, costly furnaces or and carried. to completion but the plant and pressure'vessels and sometimes involve several working costsfcan also be further considerably stages of operation and can consequently only d, e Y I i a be carried out in a troub1esome' and difficul Asoxidizing agents there may beemployedall p ul y i the w decomposition process at during the conversion. The most advantageous temperatn es'o below 00 C. is emp y doxidizing agent for. the purpose is oxygen as such A c d to this invention it hasrbeen found or in the form of air or other oxygen-containing that, by proceeding in a certain n r. alkali gases, the use oiwhich affords not'only the ad- 5 phosphates can be obtained in a simple manner antage of very great, economy but also that of v and in one op t r phoSnhorus-eontainillg extremely simple application. The introduction materials, particularly phosphorus alloys, such as of oxygen is t suitably t l passing term-phosphorus 01 the like and in this way the continuous current of 'oxygen or oxygen-corpaforementioned disadvantages and difficulties Of gaining gases during the conversion process .pref the known methods be overcome.-.This iS eflfected 'erably under a, pressure, which is higher than accord n to the invention by y g out the theprevailing vapour tension, through the conconversion, in the preparation of alkalilphos version t i f p s f o o p u t i materials in The carbon dioxide formedorset free during the presence of aqueous'alkali hydroxides or car- 't conversion process is w t advantage oxid zi g agents $11011 as oxygen 0 g mconversion container. This can, forexample, also taining gases; be effected with the aid of a current of; gas. The

In this way h adv a obtained v removal of the carbon dioxide can thus be in a the flowe PIOCeSSeS, p arly over very advantageous manner so combined with the into effect. without the addition of O y Of a containing gases that the carbon dioxide set free considerable imp v m n in the yields and above is simultaneouslycarried away with the residual all that t e fi -p p can be decomposed discharging gases. The removed carbon dioxide in relatively simple apparatus at low temperamay t be further worked up in w 45 tures and pressures. T invention accordingly ner .to liquid or solid carbon dioxide and be in affords an eco o y in plant and running costs this way obtained in a completely pure form. for the apparatus as well as a considerable econ- The temperatures and pressures pl for y in fuel- Furthermore when t n r the conversion may vary within relatively wide phosphorus according to the invention the iron 1i it Th ti h in general pro- 50 "is obtained in the form of iron oxide, which can, ceeds th m re r pidly th higher the temperafor example, be u d as a Pigment I ture and'the partial pressure of the oxygen.

The conversion is with advantage carried out According to a particular modification of theunder pressure at temperatures above C. invention the conversion process is carried out pr erably at 150 to 300 C. Instead of using in the presence of alkali-yielding phosphates, for

evolution of carbon dioxide.

ing substance, it being however, of course, also possible, if desired, to use in conjunction there-- with other alkali-yielding substances of the hereinbefore mentioned kind. When employing such phosphates, phosphates poorer in alkali, such as disodium phosphate, are obtained after the conversion, which can then, be regenerated and be thereafter again used for the conversion process. This regeneration can, for example, be effected by treating the phosphates in question with aqueous alkali carbonate or the like at ele-'- vated temperature, preferably above 100 C. and elevated pressure. In thiscase also the material is with advantage thoroughly mechanically mixed, for example, by stirring, and the carbon dioxide set free thereby removed.

It is advisable in all cases to employ the starting materials as well as the oxidizing agent in the highest possible concentration.

Examples 1. 2 parts by weight of very finely ground ferr0-' phosphorus (containing.19% of phosphorus) are mixed with 1.95 parts by weight of sodium carbonate and, after adding 20 parts of water, heated in an autoclave with thoroughstirring to 200 to 350? C. until the conversion is completed, the progress of which can be followed by 'the gen or air at .a slightly higher pressure-than that corresponding to the vapour tension at the said temperature is passed through the apparatus during the conversion, the carbon dioxide being simultaneously removed, the resulting liquor is filtered off from the residue and isthen worked up in known mannerto sodium phosphate. a 7 i 2 2 parts by weight of very finely ground ferrophosphorus (containing 19% of phosphorus) are mixed with 1.47 parts by Weight of sodiurnhydroxide and, after-adding 20 parts of Water, heated in an autoclave with thorough stirring to .200" to 350 C. until the conversion is completed. v During the conversion oxygen or air at a slightly higher pressure than thatcorresponding tothe vapour tension at the said temperature is passed into the apparatus. The resulting liquor is filtered oir from the residue and is then worked up" in known manner to sodium phosphate.

3. parts by weightof term-phosphorus, 68

parts by weight of caustic potash and 200 parts of Water are heated with the addition of oxygen" in ashaking autoclave, containing a few steel balls, toa temperature of 150 C. for six hours;

amounts to 88 to 90%."

What I claim is:

1. A process for the preparation of phosphates of the alkali-metals consisting in reacting an alloy of phosphorus with an alkali-metal compound which is alkaline in reactionin the presence of The resulting yield iof potassium phosphate A current of ox'y-' in the presence of water at an increased temperature and in the presence of an oxidizing agent.

5. Aprocess for the preparation of phosphates of the alkali-metals consisting in reacting an alloy of phosphorus with a carbonate of an alkali 'metal in the presence of water at an increased temperature and in the presence of an oxidizing agent.

6. A processfor the preparation'of phosphates of the alkali metals consisting in reacting an al'-. loy of'phosphorus with a phosphate of the alkali metal in the presence of water. at; an increased temperature and in the presence or" an oxidizing agent. c v

7. A process for the preparationof phosphates. of the alkali metals consisting in treating an alloy of phosphorus With tri-sodiu n phosphatein' the presence of water at an increased temperature and in the presence of an oxidizing agent.

8. A process as defined in claim 6 in which the phosphate, which is reacted with the alloy of phosphorus, is regenerated subsequentto its decomposition and againused in the process; 1

9. A'process as defined in claim 6 in which the: alkali metal phosphate which is reacted with'the alloy of phosphorus is regenerated with an alkaline, alkali-metal compound at an increased tern-J perature and. under increased pressure, and then utilized againin the process. f.

10. A process. as defined in claim 1 in which the reaction of the alkaline alkali metal compound with the said alloy of phosphorus resulting in the decomposition or the latter is carri d out at a temperature in excess of 100 C. and atan increased pressure.

11. A process defined in claim l in which the reaction of the alkaline alkali metal compound and the said alloy of phosphorus is accompanied by mechanical agitation of the reaction materials. 

